1. Field of the Invention
This invention relates to a switching circuit for an electric shutter in a photographic camera, and more particularly to a switching circuit for switching the supply of power to a shutter speed control circuit of an electric shutter in a camera.
2. Description of the Prior Art
In the conventional electric shutter are employed a plurality of mechanical switches provided between the power source and the shutter speed control circuit. Since in the switch means of mechanical type comprising a plurality of switches a power switch is first turned on when the main switch is turned on upon depression of a shutter release button and last turned off when the shutter release is completed. Therefore, the electric shutter employing this kind of switching means has a defect in that when some switches are turned off, electric charges move between capacitors and various circuit elements equivalent to capacitors such as diodes, PN-junction portions of transistors, operational amplifiers and so forth until the power switch is turned off last. In case that the charges move to a capacitor in a light measuring circuit and the input current of the light measuring circuit is small due to low brightness for instance, the response speed of the shutter speed control circuit is substantially lowered by the charge stored in the capacitor. Further, since the power switch is turned off last, the electric power is wasted until the power switch is turned off after the completion of shutter release.